“We are not proposing that money is taken away from farmers, simply that it should work harder, and help us to make progress on the big environmental challenges facing Wales and the world.”

Up to £30m-a-year is needed to address issues such as the continuing declines in bird species like curlews and lapwings, he said.

Without extra support, these birds will disappear from Wales within the next decade, said Mr Davies.

Farmers also need support to take action on climate change by reducing emissions of carbon from degraded soils, and holding up water in the uplands to reduce flooding.

The Assembly Government faces two possible options if it is to deliver on its environmental commitments – to redirect money currently going into the Tir Mynydd scheme or to use a new National Envelope mechanism to transfer money from farm subsidies into agri-environment schemes.

If the National Envelope was used it would effectively redistribute money from all farms in Wales to those demonstrating genuine environmental benefits – often those in more marginal, upland areas, said the charity.